Poor mileage and running rich

[fixkick]

keyon pressure is 36 and drops to 30psi on mine,

43 is max no matter what.
what matters most is the 6 PSI change from keyon to idle.
that matters big time if you go to full throttle the PSI will to down to near keyon pressure  as low as 30

why is your pressure so high?
is the return line partially blocked/ or pinched, but what matters first is the 6PSI above,

good report  so far, you have handle on what was done and what might be wrong still.

Not sure me if this year has limphome for P04xx codes, I do think not, but.... nobody knows all ECU that well.

I rechecked fuel pressure it’s at 42psi with key on and 35psi at idle. (good)
I took the entire return side of the fuel system apart and could blow air through it so that’s not restricted. 
I put about 40 miles on it with the o2 unplugged and it still runs super rich at idle possibly even worse than before. (ECU  sees that and punishes us)
Just got done running a NOID light test on the injector wiring connectors and they all blink and seem to be working normal.
Also I forgot to add that when I started trying to figure out this issue about 6 months ago the EGR passages were plugged and the intake manifold was caked with black sludge inside so I took it off and ran it through a parts washer until it was spotless inside.
I noticed today looking through the throttle body that it is starting to build up black grime inside it again. (all normal for EGR + PCV cloud of death)
EGR is dead now so is just rich fuel cloud and PCV cloud there making carbon.  The EGR main can be defeated with vacuum nipple to it unplugged and Golf tee the free hose end so it can not suck air.
I presume the injector leak down test passes?

ok FPR is ok, and no return line issues.
It is rich,
what is your OBD2 data look like, hot engine fully , a hot idle 800RPM , does 800 work and hold with head lamps on and heater blower turned on and off?
OBD2 scans.
1: closed loop. true not false.
2: LTFT?  (fuel trim)
3: ECT at 180f? or more? 300 ohms hot. (see my ect page)
4: MAF flow.    1.5–4.0 grams per second  idle hot, 800rpm,  and gunned to 2500 goes to 10-GPS. parked ,  driving looks like this (real and hills)
will your scan tool do at least this below?  (simple code readers are mostly useless) real scan tools are very useful.
5: O2 scans. below.

the engine is running rich,  I bet the scans show that too.. but I can not see them.
The fuel pressure is ok;. engine OK, exhaust man NOT OK.
O2 can fail at any time in road trip as that crack widens, then shrinks and very odd thermal dynamic actions of any crack here.

this is the super cheap scan tool (hand held) that can do even this.... act.

this is the O2 swinging, fast.  and not stuck high , not stuck low and the heater in the O2 is not dead. (sure plugged back in)
B1S1 is bank1 , s1 is front sensor, the rear is useless for fuel trim.  note the deep and full swings here and  not offset high or low. centered it is.
when the #4 exh crack widens it sucks are and this signal slams to 0v and ECU goes full on rich( LTFT way off the scale)


EGR flow, dead parked,  only moving and the large hump is the barkpressure from the cat , causing more flow via Modulator.

see this. this a PUTT,  note the negative pressure "B" a vacuum and at this point  , any crack sucks in 20 % oxygen in to said cracks, never good.



The O2 front fails for many reasons, not just bad O2, or Bad dead 02 heater

1. wrong 02 used? not the Bosch correct 4 wire? (ask)
   
2. bad wires to the 02, heater or the CELL (+-) inside. they love to burn as they hit
   
3. exhaust cracks. near front sensor 02 putt fail put fail. (luck)
   
4. the gasket at end of header, missing cracked or loose sucking in air at PUTT + B.
   
5. engine not at 180f but cold. (ECT 300 ohms hot or scan shows 180f+)
   
6. injectors leaking or   1 dead as it mindlessly pumps fresh are (engine is air pump) to 02. and it fail. (each misfire is wasted fuel)
   
7. Gross misfire, some cheap carbon spark wires even new are bad, use only MAG wires on this car and gain even better spark than stock. spark gap 0.028"
   
8. ECU stuck in limp-home mode and suspends closed loop. and runs rich; all do that. only scans find this.
   
9. MAF gone wild (rare, most go lean never seen one ever stick high) see live maf PLOTS on these post. from me. 2nd post same thread.
   

what is injector pulse widths at hot idle? 800rpm parked.  2.5 mS.

what can happen on any exhaust system not new, is cracks, come and go , some even open wider hot or hotter or fail at idle or only driving  fast.
this makes diagnosis very hard this thermal dynamic nature.

if rich at idle what is PW at injector. about 2 mS is par. 800rpm;. hot.



Make sure to use  the scan tool and click on Pending codes. for sure. see if any P03xx codes pop all are misfire.
the DTCs (many) do not set until 2 driving key off cycles pendings do not lie.
the other factoid is the DOME fuse  is blown the ECU will NOT STORE DTCs  that would be tragic here, if true.  never run with a bad DOME fuse.


now OBD2 top  #1 weakness. Misfiring.
OBD2 has only 1 O2 sensor not 4, that means if one cylinder misfires the 02 lies and the other 3 suffer.
this is #1 in my mind all the time, working OBD2. 

there are other causes,  not sure history of  any car this old.
is wrong injectors stuffed in this car, or  bought from china, junk class crap injectors, from H3LL.  
(ask  your injector pro sonic cleaning shop how they like this, (they can not use them and cores worth $0)

if ecu is  in closed loop now, at 800rpm fast idle , the exhaust  will not be black smoke but what you smell is horrible NOX gas , eats lungs up NOX.
rat nasty smell that. like back in pre 1975 cars. (epa mandated)